In recent years, there have been carried out research and development on a nanoimprint technique of preparing a mold (template or stamper) by forming a transfer ultra micropattern on a quartz substrate or the like by use of electron lithography or the like and pressing the mold with a predetermined pressure against a resist film (for example, a resist film made of a UV curable resin or a thermoplastic resin) formed on a substrate surface to be subjected to the transfer (a surface of a substrate) as an to-be-molded object, thereby transferring the transfer pattern formed on the mold. Such a technique is disclosed in the following document: Precision Engineering Journal of the International Societies for Precision Engineering and Nanotechnology 25 (2001) 192-199 (Document 1).
With reference to FIG. 24 (showing a conventional transfer method), a conventional technique will be described in detail by giving examples.
In the conventional transfer, a transfer micropattern formed on a die (mold) 101 made of, for example, quartz glass is pressed onto a substrate 105 coated with a UV curable resin (resist layer) 103, for example, and the resin 103 is cured by UV light irradiation (see FIGS. 24(a) and 24(b)). Thereafter, the die is released and a remaining film 107 is removed (see FIGS. 24(c) and 24(d)) and etching is performed (see FIG. 24(d)). Thus, a micropattern shape on the die 101, which is copied onto the resin 103, is transferred onto the substrate 105 (see FIG. 24(e)).
Incidentally, in the case of forming a transfer ultra micropattern on a die such as a quartz substrate by use of electron lithography or the like, when a portion where a transfer micropattern is to be formed has a large area, die preparation (formation of a micropattern on the die) takes a long time. An apparatus for executing the electron lithography or the like has a high man-hour cost (a cost per unit time for using the apparatus), which increases the price of the die.
Moreover, a material cost for a material such as quartz glass used as the material of the die is also high. Thus, when the portion where the transfer micropattern is formed his a large area, the die itself is increased in size, which increases the price of the die.
In this regard, the following method has been heretofore known. Specifically, when the micropattern formed on the substrate 105 has a form in which the same pattern is repeated, for example, a transfer micropattern is formed on a surface of a relatively small die. Thereafter, the transfer micropatterns are continuously transferred onto the resist layer 103 provided on the substrate 105. Thus, a continuous micropattern is formed on a large area of the substrate 105 in the same manner as the case shown in FIG. 24. The above method for forming the continuous micropattern is disclosed in Japanese Patent Application Publication No. 2006-191089 (Document 2), for example.
Incidentally, in the case of forming the continuous micropattern on a large area of the substrate by connecting the transfer micropatterns as described above, the resist layer swells up due to a first transfer, for example. Thus, there is a possibility that a second transfer continuous with the first transfer is not accurately executed.
The above situation will be described in detail by using FIG. 25 (showing a conventional transfer state). By performing a first transfer using a die M20 (101), a micropattern P11 is formed on a resist layer W21 (103). In this event, together with the micropattern P11, a swelling part W22 and the like of the resist layer W21 are formed around the micropattern F11.
In the case of attempting to form a micropattern to be connected to the micropattern P11 in a portion P12 of the resist layer W21 by a second transfer using the die M20, a shape of an end of the micropattern P11 or a shape of an end (end on the micropattern P11 side) of the micropattern formed in the portion. P12, in other words, shapes of the micropatterns at a connection between the micropattern P11 and the micropattern formed in the portion P12 is deformed by the swelling part W22. Thus, there is a possibility that an accurate micropattern cannot be formed on the resist layer W21.
For example, in the state shown in FIG. 25, when the die M20 is lowered to form a micropattern in the portion P12 of the resist layer W21, the resist layer in the swelling part W22 existing below the die M20 has nowhere to go and thus may enter into a minute concave portion existing at the end (end on the portion P12 side) of the micropattern P11.
When an accurate micropattern cannot be formed on the resist layer W21, there is a problem that a form of a micropattern to be formed on a substrate W20 (a micropattern corresponding to the micropattern formed on the substrate 105 in FIG. 24(e); a micropattern formed by etching) also becomes inaccurate.
The present invention was made in consideration of the above problems. It is an object of the present invention to provide a micropattern forming method for continuously forming micropatterns on a substrate, the micropatterns each corresponding to a transfer micropattern formed on a mold, the method being capable of forming micropatterns having an accurate form on the substrate.